This invention relates to an electron-beam writing system in lithography technique for large-scale integration (LSI) manufacturing and, more particularly, to a method of a beam size of an electron beam on writing a pattern on a sample by an electron-beam exposure of an electron-beam cell projection lithography.
In recent years, a design rule of ultra-large-scale integration (ULSI) or the minimum line width keeps on miniaturizing. It is therefore difficult to manufacture the ULSI by a conventional reduction projection exposure using ultraviolet light. In order to resolve problems in miniaturization of patterns, electron-beam (EB) direct writing technology is used for fabricating the ULSI.
However, inasmuch as the electron-beam direct writing technology carries out exposure of the pattern using a focused electron beam with one stroke, the electron-beam direct writing technology is disadvantageous in that it has poor throughput compared with that of the reduction projection exposure.
As a method of resolving the above-mentioned disadvantage, an electron-beam writing system of an electron-beam (EB) cell projection lithography is developed in resent years. Such electron-beam (EB) cell projection lithography is disclosed in, for example, an article which is contributed by Y. Nakayama et al. to J. Vac. Sci. Thechnol. B, Vol. 8, No. 6, (Nov/Dec 1990), pages 1836-1840, and which has a title of "Electron-beam cell projection lithography: A new high-throughput electron-beam direct-writing technology using a specially tailored Si aperture."
In the manner which will later be described in conjunction with FIG. 1, a conventional electron-beam writing system comprises an electron gun, a first aperture member having a primary aperture, a first deflecting arrangement consisting of a shape deflector and a selection deflector, a second aperture member having a plurality of secondary apertures, a reduction lens, and a second deflecting arrangement. The electron gun radiates an original electron beam along an electron gun axis. The first aperture member shapes the original electron beam into a primary shaped electron beam. The first deflecting arrangement deflects the primary shaped electron beam from the electron gun axis to produce a first deflected electron beam. The second aperture member shapes the first deflected electron beam into a secondary shaped electron beam. The second aperture member has, as the secondary apertures, a variable-shaped aperture for a variable-shaped electron-beam exposure and a plurality of cell projection apertures for the EB cell projection lithography. The reduction lens reduces the secondary shaped electron beam to produce a reduced electron beam. The second deflecting arrangement deflects the reduced electron beam to produce a second deflected electron beam which is irradiated on a sample.
In the variable-shaped electron-beam exposure, the shape deflector is used and the first deflected electron beam is irradiated on the variable-shaped aperture of the second aperture member. In this event, the secondary shaped electron beam shaped by the variable-shaped aperture is called a variable-shaped electron beam. In the EB cell projection lithography, the selection deflector and the first deflected electron beam is irradiated on a selected one of the cell projection apertures of the second aperture member. In this event, the secondary shaped electron beam shaped by the selected one of the cell projection apertures is called a cell projected electron beam.
In practical EB cell projection lithography, repetitious patterns are exposed using the EB cell projection lithography which nonrepetitious or random patterns touching the repetitious patterns are exposed using the variable-shaped electron-beam exposure. As a result, the repetitious patterns and the random pattern border each other at boundary sections. It is possible in the variable-shaped electron-beam exposure to make an adjustment of a beam size of the variable-shaped electron beam by using a reference mark formed on a stage. However, it is difficult in the EB cell projection lithography to correctly measure the beam size of the cell projected electron beam. As a result, in the boundary sections, size differences of the patterns formed by differences of the both beam sizes between the variable-shaped electron beam and the cell projected electron beam occur. Accordingly, the conventional electron-beam writing system is disadvantageous in that it causes degradation of reliability on fabrication of a device.